Synthetic peptides corresponding to germline T cell receptor (TCR) V beta sequences shared by encephalitogenic T cells can prevent and treat experimental autoimmune encephalomyelitis in rats. The operative mechanism apparently involves boosting of anti-TCR immunity that develops during the course of experimental autoimmune encephalomyelitis (EAE), leading to the induction of autoregulatory T cells and antibodies. Striking parallels are present between patients with multiple sclerosis and animals with EAE in the T cell frequency and TCR V gene bias of BP reactive T cells, suggesting the involvement of an encephalitogenic process in multiple sclerosis. Preliminary trials with the appropriate human TCR peptides indicate that anti-TCR immunity can be boosted efficiently and safely, with concomitant loss of BP response, thus providing an effective strategy for selective regulation of autoimmunity in man.